Incorporation of thrombospondin into fibrin clots
Thrombospondin is a major platelet glycoprotein which is released from platelets during blood coagulation. The authors examined the interaction of thrombospondin with polymerizing fibrin. Thrombospondin, purified from human platelets and labeled with /sup 125/I, became incorporated into clots formed from both plasma and purified fibrinogen. Plasma clots contained somewhat less thrombospondin than clots formed from equivalent concentrations of fibrinogen. In plasma clots and fibrin clots formed in the presence of factor XIII, thrombospondin was cross-linked in the clot; thrombospondin in the supernatant remained largely monomeric. Cross-linking of thrombospondin by factor XIII, however, only slightly increased the amount of thrombospondin which was incorporated into the clot. In contrast, incorporation of /sup 125/I-fibronectin into clots was dependent upon cross-linking. Most of the incorporation of /sup 125/I-thrombospondin occurred during fibrin polymerization as judged by parallel studies of the incorporation of /sup 125/I-fibrinogen. The amount of thrombospondin incorporated into a clot was directly related to thrombospondin concentration and was only weakly dependent on fibrinogen concentration. Incorporation was not saturated at thrombospondin:fibrin (mol/mol) ratios as high as 2/1. Thrombospondin, however, modified the final structure of fibrin clots in a concentration-dependent manner as monitored by opacity. When tryptic digests of /sup 125/I-thrombospondin were studied, the 270-kilodalton core became incorporated into fibrin whereas the 30-kilodalton heparin binding fragment was excluded. These results indicate that thrombospondin specifically co-polymerizes with fibrin during blood coagulation and may be an important modulator of clot structure.
- OSTI ID:
- 6241080
- Journal Information:
- J. Biol. Chem.; (United States), Vol. 12
- Country of Publication:
- United States
- Language:
- English
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551001* - Physiological Systems- Tracer Techniques